1 The word dinosaur means "terrible lizard." They appeared on earth about 230 million years ago. What were these strange reptiles that lived during the Mesozoic Era? What did they look like? What did they eat?2 Dinosaurs were a special group of reptiles. They came in all sizes and shapes. They had a different posture than most reptiles. Dinosaurs' legs were set directly underneath their bodies. Some even walked on two legs.3 The largest complete dinosaur found so far was Brachiosaurus. It was about 25 meters long and over 10 meters high. This is about as long as two school buses, and as high as a four story building!